Vacuum-tube circuits



June 9, v1925. 1,541,311

s. E. ANDERSON VACUUM TUBE CIRCUITS Filed FebL v. 192s SDNEY E. ANDERSON, F BROOKLYN, YORK, SSGNOB T0 WESTERN ELECTRIC COMPANY, INCORPORATED, 0F NEW YORK, N. Y., A CORPORATION 0E NEW YORK.

.vacuum-TUBE l cmcurrs. v

Application led February To allwlwmitmayconcem:

Be it known that I, SIDNEY E. ANDER- soN, a citizen of the United States, residing at Brooklyn, in the county of Kings, State of New York, have invented certain new and useful Improvements in Vacuum- Tube Circuits, of which the following is a full, clear, concise, and exact description.

This invention relates to three-electrode vacuum tube circuits and has for its object to stabilize the operation of vacuum tube circuits, employing a variable source of potential.

In certain uses of vacuum tubes where exact adjustments are necessary, slow changes in a source of potential, if not correct, may give rise to series diiculties. It is also at times desirable to energize vacuum -tubes with pulsating electromotive forces such,

lfor example, as are'derived from rectified alternating currents and if the frequency of the pulsations are of the same order of magnitude as frequencies to be transmitted, interference will result.

The invention aims to provide for using variable electromotive forces for energizing the vacuum tube Iand without disturbing the proper operation of the circuit.

In accordance with the invention the variable electromotive force isl so connected that while one ortion of its potential is applied between t e cathode and anode of the vacuum tube, another portion of opposite phase and of a value one over the amplification factor of the tube times the anode potential is applied to the grid or control electrode.

As is well known, a potential applied to the .grid is substantially equivalent to applying a potential to the anode of a value p. times the grid potential, where p. re resents the amplification factor. The e ect of the above arrangement is therefore that when the source of potential is changed,L equal and opposite effects are applied to the vacuum tube and no change in the space current results.

In case an appreciable normal space current is desired it is necessary to apply an additional xed potential to the grid 1n order to permit space current to ow. For rectification or detection, however, normally zero space current may be desirable.`

variable source of electromotive force 10 is connected across resistance path 12, the posltlve terminal of the resistance being connected to the anode 4 through the primary of transformer 7 and the negative ter-f 7'0 minal being connected to the grid throu h the secondary of transformer 6. The cat ode is connected to the resistance 12 at a point dividing it into portions 12a and 12b,

the values of which are so related to each other and to the internal impedance of the vacuum tube that the potential drops there across have the values respectively, where E is the value of source 10 and p. is the amplification factor of the tube. The variable source of electromotive force- 10 may be a battery subject to slow variations due' to the charge and discharge cycle, as shown in the figure, or some form of rectier which supplies a pulsating unidirectional current, or a generator, in which case there is superimposed upon the constant electromotive force of the generator a e u times the impedance of condenvolts more negative. Since this change is the equivalent of u times (if) i volts in the plate circuit, it is seen that there will be no change in the space current. Thus, the invention insures that the space current will remain essentially constant over a Wide range of variations in the potential of source 10. The internal impedance of tube 1 may be regarded as a constant resistance over a considerable range of voltages especially it resistances 12l and 12b are relatively small.

The range of voltages over which stable operation may be obtained may be increased by including in the resistance 12b a. resistance having a positive coeiiicient of resistance such, for example, as iron or by including in the resistance 12a a resistance havirg a negative coefficient of resistance such, for example, as carbon or boron. This may be explained by the fact that the plate impedance of a. vacuum tube decreases as the plate voltage increases, and therefore, the plate current with increasing plate voltage increases at a greater rat'e than does the voltage. If the portion 12b of theresistance is of some material whose resistance increases with temperature and therefore with the voltage applied to its terminals, this increase in resistance may be adjusted so as to vcompensate for the decrease in plate impedance, the total impedance between the cathodes and anode thus remaining constant. Similarly, if the portion 12a ofthe resistance is composed of a materialhaving a negative coefficient of resistance, and the plate voltage increases,A the dro across 12a decreases, and the decrease in t e voltage applied to the grid serves to compensate for the decreased plate impedance. If the resistance 12a be made to have approximately the same resistance characteristic as that of the anodecathode impedance, resistance 12b may be omitted.

While only one embodiment of the invention has been shown and described, it is obvious that the invention may assume other forms -withing the scope of the appended claims.

What is claimed is:

1. A vacuum tube translating device having'a cathode, an anode, and a control electrode, a variable source of potential for energizing said device connected to said cathode, means for applying potentials of opposite phase and havlng a ratio of one over the amplification factor of'said tube to sald control electrode and said anode respectively, and means for impressing on said device voltage variations to be repeated.

v2. vacuum tube translating device havi ing a cathode, an anode and a control elecpotential for said device, a resistance path connected across said source, connections.

'vice voltage variations to be repeated.

3. A vacuum tube translating device having a cathode, an anode and a control electrode, a variable source of space current potential for said device, a resistance path connected across said source, connections from said path to said electrodes respectively at such points that the'potential applied to said anode is opposite in phase and p. times the potential applied to said control electrode, an additional source of potential in series with said control electrode, and means for impressingon said device voltage variations to be repeated.

4f. The method of controlling the space current in a vacuum tube having a cathode, an anode, and a control electrode which comprises applyin between said cathode and anode a varia le potential, simultaneously applying between said cathode and control electrode a potential opposite in phase and equal to u times said first potential, and simultaneously impressing on said vacuum tube potential variations to be transmitted thereby.

5. The method of operating a vacuum tube having a cathode, an anode and a control electrode, which comprises applying to said control electrode and said anode respectively, two potentials derived from a common source and of such relative values that their combined effects on the space current are substantially zero, applying an addi'- tional potential to said control electrode, and simultaneously impressing on said vacuum tube potential variations to be transmitted thereby.

6. The method' 'of operating a vacuum tube having a cathode, an anode and a control electrode, which comprises applying to said control electrode and said anode respectively, two potentials derived from a common source and of such relative values that their combined effects on the space current trode, a variable source of space current are substantially zero, applying an additionall potential to said control electrode, and simultaneously impressing on said vacuum vtube potential variations to be transmitted thereby.

In witness whereof, I hereunto subscribe my name this 30th day of January A. D.,

SIDNEY E. ANDERSON. 

